Research On Robustness Of Long-span Spatial Lattice Structure

The research on the problems of structural robustness derives from the Ronan Point Apartment building because the southeast corner of the building collapse from top to bottom since gas explosion leads the local damage in London in1968. In the "9.11" accident, the World Trade Center was attacked by the terrorist and the continuous collapse was paid more attention by scholars and engineers about the problems of structural robustness. Although many scholars at home and abroad present robustness index based on the structural properties and performance, each one has its defects. Therefore, the academic research on the quantitative index to measure the structural robustness has not yet reached agreement.The paper presents the kinetic equation of long-span spatial lattice structure under dynamic loads can be transformed into the state space equation. Using the matrix theory in modern control theory, we can explain the structural robustness and judge the sensitivity of structural response for the perturbation of the matrix elements. Finally, we can put forward the structural robustness index. In terms of the long-span spatial lattice structure, when the value of R(AA) is smaller, the structural robustness becomes better. From the long-span spatial lattice structure in this paper, the longitudinal bars of upper and bottom chord bars have a greater impact on the structural robustness. Meanwhile, web members which are closer to support also have a greater impact on the structural robustness. The paper introduces the residual influence factor analyze the structural robustness index and verify its accuracy.Three basic algorithms are proposed to solve the problem of calculating the structural dynamic response under the initial damage:general method, iterative method and exact solution. Although using the dynamic analysis method to research on the structural robustness can obtain the most accurate result, it will also inevitably face with the low computational efficiency and high computational complexity problems. Therefore, when introducing the load increase factor and dynamic increase factor, using static analysis instead of dynamic analysis method may become an effective and simplified calculation method to research on the structural robustness. In terms of specified space truss, the paper gives the reference value1.2～1.6about the load increase factor and dynamic increase factor.The design of structural robustness not only needs to be calculated from quantitative analysis, but also needs to strengthen the structural robustness from qualitative analysis. For example, to improve the ductility of the member, to strengthen the construction of grid structure and reliable connection; to gain the many load transfer paths; incremental redundancy and so on, which ensure the long-span spatial lattice structure is robust enough further.